CN112573503B - Preparation method of nitrogen-doped porous carbon material, prepared porous carbon material and application thereof - Google Patents

Abstract

The invention discloses a preparation method of a nitrogen-doped porous carbon material, which relates to the technical field of nano material preparation, and comprises the following steps: (1) preparing a yellow precursor; (2) heating and carbonizing the yellow precursor at 600-700 ℃ for 2h at the speed of 10 ℃/min in a nitrogen atmosphere to obtain a black sample; (4) ultrasonically dispersing a black sample in deionized water, and then adding mixed acid for reflux etching; (5) and washing and drying the sample subjected to the reflux etching to obtain the nitrogen-doped porous carbon material. The invention also provides the material prepared by the method and application thereof. The invention has the beneficial effects that: the preparation method is safe and easy to implement, has short synthesis period, and can be used for mass preparation and is expected to be popularized and applied industrially.

Description

Preparation method of nitrogen-doped porous carbon material, prepared porous carbon material and application thereof

technical field

The invention relates to the technical field of nanomaterial preparation, in particular to a preparation method of a nitrogen-doped porous carbon material, the prepared porous carbon material and applications thereof.

Background technique

Lithium-ion batteries are an energy storage system for portable electronic devices with high energy and power density. However, geographic constraints and the increasing cost of lithium resources greatly hinder its potential for future applications. Considering the uneven distribution of lithium resources and the scarcity of lithium resources in the earth's crust (20 ppm), it is desirable to develop rechargeable metal-ion batteries based on low-cost and earth-abundant elements such as sodium (23,000 ppm) potassium (17,000 ppm). Furthermore, sodium and potassium share similar physicochemical properties and electrochemical reaction mechanisms with lithium, making SIBs and KIBs promising alternatives to LIBs. Therefore, it is crucial to explore reversible anode materials with suitable structures for high-performance potassium-ion batteries.

So far, a lot of work has been done on the design of potassium ion anode materials at home and abroad, such as sulfides, selenides, phosphides, and carbonaceous materials. Among them, carbonaceous materials have become attractive anodes for KIBs due to their environmental protection, low cost, and abundant content. To date, one of the effective strategies to improve the potassium storage performance of carbonaceous materials is to tune more active sites for adsorbing potassium. However, few studies have focused on the ultra-potassium storage formed by nanopores decorated with a large number of N atoms on the inner surface. ability.

Patent application with publication number CN110002424A discloses nitrogen and oxygen co-doped porous carbon material, preparation method and application thereof. Precursors are prepared by cobalt nitrate and 2-methylimidazole at room temperature, and then black materials are obtained by calcining the precursors in nitrogen. Then, the above black material is treated by hydrothermal oxidation, and finally the obtained material is refluxed with nitric acid to obtain a diatomic doped carbon material, that is, a nitrogen and oxygen co-doped porous carbon material. However, the prepared nitrogen and oxygen co-doped porous carbon materials have poor stability.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is that the nitrogen and oxygen co-doped porous carbon materials in the prior art have poor stability, and a preparation method of nitrogen-doped porous carbon materials is provided.

The present invention realizes and solves the above-mentioned technical problems through the following technical means:

A preparation method of nitrogen-doped porous carbon material, comprising the following steps:

(1) Dissolve nickel chloride in methanol at room temperature to form solution A, dissolve polyvinylpyrrolidone and 2-methylimidazole in methanol to form solution B, then mix solution A and solution B under stirring Then, let stand for 24h; the concentration of nickel chloride is 13.3-16.3mg/mL, the concentration of polyvinylpyrrolidone is 16.7-30mg/mL, and the concentration of 2-methylimidazole is 21.9-32.8mg/mL;

(2) centrifuging the mixed solution in step (1), washing and drying the centrifuged product to obtain a yellow precursor;

(3) heating and carbonizing the yellow precursor in step (2) at a rate of 10°C/min for 2h at 600-700°C in a nitrogen atmosphere to obtain a black sample;

(4) ultrasonically dispersing the black sample in deionized water, and then adding mixed acid for reflux etching;

(5) Washing and drying the sample after reflow etching, that is, obtaining a nitrogen-doped porous carbon material.

Beneficial effects: the present invention adopts nickel chloride and 2-methylimidazole to prepare precursors at room temperature, and in the preparation process, polyvinylpyrrolidone is used as surfactant, the amount of methanol is adjusted, and the formed precursors are nanospheres composed of sheets , the carbon material formed by etching is a hollow carbon material with a hollow crisp porous structure, and a large number of edge-doped nitrogen atoms are doped on the surface of the nanopore, which provides a large number of active sites for the adsorption of K ⁺ , shortening the electron and The diffusion distance of K ⁺ , when used as a negative electrode material, has high specific capacity and good cycle stability, especially in the process of charging and discharging at a large current of 5A/g, after 10,000 cycles, it can maintain 167mAh/g.

In the process of calcining the precursor, a large amount of carbon dioxide and water molecules will overflow, resulting in the finally obtained nitrogen-doped porous carbon material having a loose and porous composite structure. The process for preparing the nitrogen-doped porous carbon material according to the invention is simple and efficient, safe and feasible, and has a short synthesis period, and is expected to be popularized and industrialized.

The precursor in the present invention cannot be obtained without adding polyvinylpyrrolidone in the preparation process, and after adding the precursor, the morphology becomes a spherical object composed of nanosheets. If the amount of methanol is too small, nickel chloride and 2-methylimidazole cannot be dissolved, and too much will cause waste.

Preferably, the centrifuged product is washed with methanol and then dried at 60°C for 6h.

Preferably, the mixed acid in the step (4) is hydrochloric acid and nitric acid, and the volume ratio of the hydrochloric acid and nitric acid is 1:1.5.

Preferably, the reflow etching temperature is 80° C., and the reflow etching time is 6 h.

Preferably, deionized water and ethanol are respectively used for washing in the step (5).

Preferably, the drying temperature in the step (5) is 60° C., and the drying time is 6 h.

The present invention also provides a nitrogen-doped porous carbon material prepared by the above method, wherein the nitrogen-doped porous carbon material has a hollow porous structure.

Beneficial effects: The crisp porous structure is conducive to the entry and exit of potassium ions and electrolytes into and out of the active material; the hollow porous and larger specific surface area structure can increase the contact area between the electrode material and the electrolyte, and shorten the diffusion distance between lithium ions and the electrolyte; high nitrogen atoms The doping can improve the conductivity of the entire carbon material. When used as a negative electrode material, it has high specific capacity and good cycle stability, especially in the process of charging and discharging at a large current of 5A/g, after 10,000 cycles, it can maintain 167mAh/g.

Preferably, the nitrogen-doped porous carbon material has a specific surface area of 313-501 m ² /g.

The present invention also provides an application of the nitrogen-doped porous carbon material prepared by the above method as a negative electrode material of a potassium ion battery.

Beneficial effects: When used as a negative electrode material, it has high specific capacity and good cycle stability, especially in the process of charging and discharging at a large current of 5A/g, after 10,000 cycles, it can maintain 167mAh/g.

Preferably, the preparation method of the potassium ion battery negative electrode material includes the following steps: mixing nitrogen-doped porous carbon material, acetylene black and polyvinylidene fluoride into a slurry-like substance, and then coating the slurry-like substance on the copper foil, After drying, electrode sheets were prepared.

The present invention also provides an application of the nitrogen-doped porous carbon material prepared by the above preparation method in preparing a lithium ion battery.

Beneficial effects: the present invention uses nitrogen-doped porous carbon material to obtain a lithium ion battery, and the test battery can still maintain a discharge capacity of 279mAh/g after 2000 cycles at a current density of 1A/g. During the charging and discharging process of 5A/g, it can maintain 167mAh/g after 10,000 cycles.

The advantages of the present invention are: the present invention adopts nickel chloride and 2-methylimidazole to prepare the precursor at normal temperature, and in the preparation process, polyvinylpyrrolidone is used as the surfactant, the amount of methanol is adjusted, and the formed precursor is composed of flakes The carbon material formed by etching is a hollow carbon material with a hollow and loose porous structure, and a large number of edge-doped nitrogen atoms are doped on the surface of the nanopore, which provides a large number of active sites for the adsorption of K ⁺ , shortening the the diffusion distance of electrons and K ⁺ .

In the process of calcining the precursor, a large amount of carbon dioxide and water molecules will overflow, resulting in the finally obtained nitrogen-doped porous carbon material having a loose and porous composite structure. The process for preparing the nitrogen-doped porous carbon material according to the invention is simple and efficient, safe and feasible, and has a short synthesis period, and is expected to be popularized and industrialized.

When used as a negative electrode material, it has high specific capacity and good cycle stability, especially in the process of charging and discharging at a large current of 5A/g, after 10,000 cycles, it can maintain 167mAh/g.

Compared with the prior art, the synthesis steps at room temperature are simpler and the yield is high, and the material is more suitable for potassium anode materials, which have higher requirements on materials, the small current specific capacity reaches 409mAh, and the number of cycles is 200 cycles. , the high current of 5A/g is still stable after 10000 cycles, and the rate performance is good, and it can reach 244mAh g ^-1 under the current density of 5A/g.

Description of drawings

1 is a scanning electron microscope image of the nitrogen-doped porous carbon material at a temperature point of 600° C. in Example 1 of the present invention; the scale bar of a is 1 μm, and the scale bar of b is 200 nm.

2 is a transmission electron microscope image of the nitrogen-doped porous carbon material at a temperature point of 600° C. in Example 1 of the present invention; the scale bar of c is 100 nm, and the scale bar of d is 200 nm.

3 is a high-resolution transmission electron microscope image of the nitrogen-doped porous carbon material at a temperature point of 600° C. in Example 1 of the present invention; the scale bar of e is 20 nm, and the scale bar of f is 100 nm.

4 is a transmission electron microscope image of the nitrogen-doped porous carbon material at a temperature point of 700° C. in Example 1 of the present invention; the scale bar of a is 0.2 μm, and the scale bar of b is 200 nm.

5 is the X-ray diffraction pattern of the nitrogen-doped porous carbon material at temperature points of 600 and 700°C in Example 1 of the present invention; the temperature point of a is 600°C, and the temperature point of b is 700°C.

6 is a Raman diagram of the nitrogen-doped porous carbon material at temperature points of 600 and 700°C in Example 1 of the present invention; the temperature point of a is 600°C, and the temperature point of b is 700°C.

7 is an X-ray photoelectron spectrum diagram of the nitrogen-doped porous carbon material at temperature points of 600 and 700° C. in Example 1 of the present invention;

8 is the adsorption-desorption curve diagram of the nitrogen-doped porous carbon material at temperature points of 600 and 700°C in Example 1 of the present invention; the temperature point of a is 600°C, and the temperature point of b is 700°C.

Fig. 9 is the half-cell discharge capacity and cycle number curves obtained from the nitrogen-doped porous carbon material at the temperature points of 600 and 700°C in Example 2 of the present invention; wherein the discharge current density is 100 mA/g, the temperature point of a is 600°C, and the temperature point of b is 600°C. The temperature point is 700°C.

Fig. 10 is the half-cell discharge capacity and cycle number curve obtained in Example 2 of the present invention, wherein the discharge current density is 1A/g;

11 is the capacity and cycle curves of the half-cell obtained from nitrogen-doped porous carbon material at different discharge current densities at temperature points of 600 and 700°C in Example 2 of the present invention; the temperature point of a is 600°C, and the temperature point of b is 700°C.

12 is the discharge capacity and cycle times curves of the half-cell obtained from the nitrogen-doped porous carbon material at the temperature points of 600 and 700° C. in Example 2 of the present invention; the discharge current density is 5 A/g.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the present invention. examples, but not all examples. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The test materials and reagents used in the following examples can be obtained from commercial sources unless otherwise specified.

If the specific technology or condition is not indicated in the embodiment, it can be carried out according to the technology or condition described in the literature in this field or according to the product specification.

Example 1

The preparation method of nitrogen-doped porous carbon material comprises the following steps:

(1) At room temperature, dissolve 237 mg of nickel chloride in 15 mL of methanol to form solution A; dissolve 300 mg of polyvinylpyrrolidone and 328 mg of 2-methylimidazole in 15 mL of methanol to form solution B, and stir the solution A and solution B are slowly dripped together. After stirring the mixture for 5 minutes, it was left to stand at room temperature for 24 hours.

(2) The prepared samples were centrifuged, washed three times with methanol, and then dried in an oven at 60° C. for 6 h to obtain a yellow precursor.

(3) Then, the prepared precursors were carbonized for 2 h at a heating rate of 10°C/min under the conditions of 600°C and 700°C in a nitrogen atmosphere to obtain two black samples.

(4) ultrasonically disperse the above black sample into 30 ml of deionized water, and then add 10 mL of hydrochloric acid and 15 mL of nitric acid to the solution. The resulting solution was transferred to a 100 ml round bottom flask and kept at reflux for 48 hours at 80°C.

(5) The product was centrifuged, washed three times with deionized water and ethanol, and then dried in a 60°C oven for 6 hours to obtain a nitrogen-doped porous carbon material with a temperature of 600°C and a nitrogen-doped porous carbon material with a temperature of 700°C, respectively. Porous carbon material.

Figures 1 to 3 are respectively a scanning electron microscope (SEM) photograph, a transmission electron microscope (TEM) photograph and a high resolution transmission photograph (HRTEM) of the final product obtained in this example at a temperature of 600°C. It can be seen from the SEM images of Figure 1(a, b) that the final product prepared is composed of a large number of spherical particles with a particle size between 50 and 100 nm. It can be seen from the TEM images of Fig. 2(c, d) that the as-prepared polyhedrons contain a large number of holes. These voids are caused by the release of large amounts of small molecular gases (such as nitrogen dioxide, carbon dioxide, and water molecules) during the carbonization process. It can be seen from the HRTEM images of Fig. 3(e,f) that the as-prepared polyhedrons contain a large number of obvious lattice fringes of carbon materials. Figure 4 shows the transmission electron microscope at the temperature point of 700 °C, which is also similar to the spherical particle and the temperature point of 600 °C.

图。从图5a 5b中可以看出，图中25°左右的衍射峰是碳材料典型(002)晶面的衍射峰。此外，25°处的峰比较强且宽，可归因于氮和掺杂多孔碳材料的结晶性比较好。所得复合材料的石墨化程度可以通过拉曼光谱来确定。Fig. 5 X-ray diffraction of the final product obtained in this example

picture. It can be seen from Figures 5a and 5b that the diffraction peak around 25° in the figure is the diffraction peak of the typical (002) crystal plane of carbon materials. In addition, the peak at 25° is relatively strong and broad, which can be attributed to the better crystallinity of nitrogen and doped porous carbon materials. The degree of graphitization of the resulting composites can be determined by Raman spectroscopy.

FIG. 6 is a Raman spectrogram of the final product obtained in this example. It can be seen from the Raman spectrum that the two peaks at 1350 and 1580 cm ^-1 can be assigned to the typical D and G bands of carbon materials, respectively.

FIG. 7 is an X-ray photoelectron spectrogram of the final product obtained in this example. It can be seen from the X-ray photoelectron spectrum that the final product contains three atoms of carbon, nitrogen and oxygen, further indicating that nitrogen-doped carbon materials are prepared. In addition, the results of X-ray photoelectron spectroscopy also showed that the atomic ratios of nitrogen and oxygen at the temperature point of 600 °C in the final product were 8.49 and 14.31%, respectively, while the atomic ratios of nitrogen and oxygen at the temperature point of 700 °C were 6.20 and 13.22%, respectively.

FIG. 8 is a nitrogen adsorption-desorption curve diagram of the final product obtained in this example. From the nitrogen adsorption-desorption curve, it can be seen that the nitrogen-doped carbon material at the temperature point of 600 °C has a porous structure with a specific surface area of 500.58 m ² /g, while that at 700 ° C has a specific surface area of 313.97 m ² /g.

Example 2

Using the nitrogen-doped porous carbon material in Example 1 to prepare a potassium ion battery negative electrode material, the specific steps include:

The nitrogen-doped porous carbon material was mixed with acetylene black and polyvinylidene fluoride PVDF in a mass ratio of 80:10:10 to make a slurry, and then the slurry was coated on copper foil and dried in an oven at 80 °C. After drying, cut the copper foil into circular electrode pieces with a diameter of 14mm, which is the negative electrode material of the lithium ion battery.

Example 3

The potassium ion battery is prepared by using the potassium ion battery negative electrode material in Example 2, which specifically includes the following steps:

Take the electrode sheet in Example 2 as the positive electrode, take the circular metal potassium sheet with a diameter of 14 mm as the negative electrode, and use the mixture of ethylene carbonate EC and diethyl carbonate DEC in a mass ratio of 1:1, containing a concentration of The mixed solution of 3 mol/L bisfluorosulfonimide potassium salt KFSI was used as the electrolyte, and the circular polypropylene film with a diameter of 16 mm was used as the diaphragm, and a button battery was assembled in a glove box protected by an argon atmosphere as a test. Battery.

Test it for Neware BTS-610 using a battery test system. As shown in Fig. 9(a), when the temperature point is 600 °C and the current density is 100 mA/g, the discharge capacity remains at 409 mAh/g after 200 cycles.

As shown in Figure 10, under the current density of 1A/g, the discharge capacity of the test battery can still be maintained at 279mAh/g after 2000 cycles.

Figure 11(a) The rate test is also an important parameter to measure the stability of a battery. The half-cells prepared in this example were tested at current densities of 0.1, 0.2, 0.4, 0.6, 0.8, 1, 2, and 5 A g ^-1 , respectively, and their specific capacities were 480, 451, 417, 398, 376, 345, 307 and 244 mAh g ^-1 , respectively.

Figure 9(b) When the temperature point is 700°C, the discharge capacity remains at 377mAh/g. Figure 11(b) shows the test cells with current densities of 0.1, 0.2, 0.4, 0.6, 0.8, 1, 2, and 5A g ^-1 , and their specific capacities are 375, 293, 247, 221, 204, 188, 162 and 87 mAh g ^-1 , respectively. The results show that, The half-cell in this embodiment has good stability.

Figure 12 shows that during the charging and discharging process of 5A/g, after 10,000 cycles, it can maintain 167mAh/g.

The above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The recorded technical solutions are modified, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (8)

1. a preparation method of nitrogen-doped porous carbon material, is characterized in that: comprise the following steps: (1) Dissolve nickel chloride in methanol at room temperature to form solution A, dissolve polyvinylpyrrolidone and 2-methylimidazole in methanol to form solution B, then mix solution A and solution B under stirring Then, let stand for 24h; the concentration of nickel chloride is 13.3-16.3mg/mL, the concentration of polyvinylpyrrolidone is 16.7-30mg/mL, and the concentration of 2-methylimidazole is 21.9-32.8mg/mL; (2) centrifuging the mixed solution in step (1), washing and drying the centrifuged product to obtain a yellow precursor; (3) heating and carbonizing the yellow precursor in step (2) at a rate of 10°C/min for 2h at 600-700°C in a nitrogen atmosphere to obtain a black sample; (4) ultrasonically dispersing the black sample in deionized water, and then adding mixed acid for reflux etching; (5) washing and drying the sample after reflux etching to obtain nitrogen-doped porous carbon material; The mixed acid in the described step (4) is hydrochloric acid and nitric acid, and the volume ratio of the hydrochloric acid and nitric acid is 1:1.5; The reflow etching temperature was 80° C., and the reflow etching time was 6 h. 2 . The preparation method of nitrogen-doped porous carbon material according to claim 1 , wherein the centrifuged product is washed with methanol, and then dried at 60° C. for 6 hours. 3 . 3 . The method for preparing nitrogen-doped porous carbon material according to claim 1 , wherein in the step (5), deionized water and ethanol are respectively used for washing. 4 . 4 . The method for preparing nitrogen-doped porous carbon material according to claim 1 , wherein the drying temperature in the step (5) is 60° C. and the drying time is 6 h. 5 . 5 . A nitrogen-doped porous carbon material prepared by the preparation method according to claim 1 , wherein the nitrogen-doped porous carbon material has a hollow porous structure. 6 . 6. An application of the nitrogen-doped porous carbon material prepared by the preparation method according to any one of claims 1 to 4 as a negative electrode material for potassium ion batteries. 7. The application of the nitrogen-doped porous carbon material as claimed in claim 6 as a potassium ion battery negative electrode material, wherein the preparation method of the potassium ion battery negative electrode material comprises the following steps: the nitrogen-doped porous carbon material, Acetylene black and polyvinylidene fluoride are mixed to form a slurry, and then the slurry is coated on the copper foil, and after drying, the electrode sheet is prepared. 8. An application of the nitrogen-doped porous carbon material prepared by the preparation method according to any one of claims 1 to 4 in the preparation of lithium ion batteries.

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